<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
<script type="text/javascript" src="js/jquery-1.12.4.min.js"></script>
<script type="text/javascript">
		var request = new XMLHttpRequest();
		function userErr() {
			request.open("post", "CheckUserServlet", true);
			request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
			request.send("op=check&userName=" + $("#userName").val());
		}
		request.onreadystatechange = function (ev) {
	    	if (request.readyState == 4 && request.status == 200) {
	       		$("#err").html(request.responseText);
	    	}
		};
</script>
</head>
<body>
	用户名:<input type="text" id="userName" name="userName" id="userName" onblur="userErr()"><span id="err"></span><br/>
</body>
</html>